The present invention relates to a cap and connector device and particularly to a cap and connector with an improved cable clamp. More specifically, it relates to an insulating clamp for a cable which clamp forms part of a cap or connector and permits the insulated clamping of a cable immediately adjacent the terminal end of the cable where it is connected to such a cap or connector.
It is well known that caps and connectors are employed to provide temporary connection between electric power supplies and apparatus which uses the electric power. The conductors of such cables are connected at at least one end to a cap or connector and specifically to electrical contacts provided in the caps and connectors. A patent, U.S. Pat. No. 3,461,417, issued to the same assignee as this application discloses such a cap and connector structure. U.S. Pat. No. 3,360,766 teaches an improved metal clamp. This patent teaches a cap and connector with a metal cable clamp such as has been used on wiring devices for many years. The present invention concerns such a cap and connector structure and particularly the clamp portion where the clamp is itself insulating and yet provides the strain relief function normally performed by metal clamps used in connection with such caps and connectors.
For some time, the use of caps and connectors has involved a grounding attachment for connection to such cable clamps and such a grounding feature is taught in the above referenced U.S. Pat. No. 3,461,417. However, there are some situations in which the presence of any metal on the external portion of the cap or connector particularly where a hand grip of the cap or connector might be obtained is deemed less desirable than a more insulating form of clamp.
Recently, there has been developed in the wiring device industry a number of such insulating cable clamps or strain relief clamps. Many of these are attached by the bringing together of two half portions, i.e. two halves of the insulated strain relief clamp members, and by the use of metal screws to attach these two halves together. One such insulating cord grip is taught in U.S. Pat. No. 3,779,593 and another in U.S. Pat. No. 3,437,980. Several others are also known. Generally, the cord clamps are intended for use in attaching cables of a relative wide range of wire sizes as the caps and connectors are used in conducting electric power of different amperages and voltages and phases. Where such a wide range of electric power types and levels are to be employed, the cables used in these applications vary not only as to size of the individual internal conductors, but vary also as to the number of conductors in the cable and the overall size of the cable including the outer jacket of the cable.
In addition, a number of patents concerned with cable clamping in connection with cable termination in caps and connectors have been disclosed in the patent art. Some patents which disclose such articles include U.S. Pat. Nos. 3,430,187; 3,865,461; 3,667,783; 3,624,591; 1,882,856; and 1,181,451; and British Pat. No. 165 issued 1899 and British Pat. Nos. 876,293 and 905,455; and also German Pat. No. 1,489,532.
One of the problems found with respect to the effectiveness of cable clamps for cable termination in caps and connectors is the limitation of sizes or the limitation of the range of diameters of the cables which are usable in connection with such clamps. Generally, it is found that the range of cable sizes is limited by the overall diameter of the clamp itself. Alternatively, it has been found necessary to use some form of adaptor in increasing the size range of clamps to make sure that cables of a wider range of sizes can be clamped. The need for use of such adaptors with prior art clamps relates to the range of cable diameters expected to be used in connection with clamps and with caps and connectors for which such clamps are used. One such cable clamp which employs adjustable adaptor is U.S. Pat. No. 3,624,591. Another form of cable clamp employing adaptors is the clamp of a cap and connector of Leviton manufacture. Where such adaptors are not employed, there is a tendency for some of such clamps to develop uneven perimeters as they are expanded to hold larger diameter cable so that it is not feasible to use two such clamps in conventional duplex receptacles where such caps are plugged into wall receptacles to obtain power to feed the cable attached to the wiring device.
A patent which discloses a cable clamp made of insulated material which has a narrow range of cable sizes which can be held by the clamp is the U.S. Pat. No. 3,667,783 of Sotolongo.